Paperback spine thickness by page count
The maker draws your spine from these figures. They are Amazon KDP’s own published per-page numbers (white paper 0.002252 in, cream paper 0.0025 in) multiplied by the page count. Checked against KDP’s help page on 9 October 2026.
| Pages | White paper (in) | White paper (mm) | Cream paper (in) | Cream paper (mm) |
|---|
| 100 | 0.225 | 5.7 | 0.250 | 6.4 |
| 150 | 0.338 | 8.6 | 0.375 | 9.5 |
| 200 | 0.450 | 11.4 | 0.500 | 12.7 |
| 250 | 0.563 | 14.3 | 0.625 | 15.9 |
| 300 | 0.676 | 17.2 | 0.750 | 19.1 |
| 350 | 0.788 | 20.0 | 0.875 | 22.2 |
| 400 | 0.901 | 22.9 | 1.000 | 25.4 |
| 450 | 1.013 | 25.7 | 1.125 | 28.6 |
| 500 | 1.126 | 28.6 | 1.250 | 31.8 |
| 600 | 1.351 | 34.3 | 1.500 | 38.1 |
Source: Amazon KDP Help, Paperback cover. KDP says a paperback needs at least 79 pages to carry text on the spine. Millimeters are inches × 25.4, rounded half up to one decimal.
Questions, asked often
Is this book mockup maker really free?
Yes. There is no watermark, no account and no download limit. You get a PNG or JPG of your cover on a 3D paperback, hardcover, series, box set, e-reader, tablet or phone.
Is my cover uploaded anywhere?
No. Your browser reads the image and draws the mockup on your own device. Your cover is never sent to us or to anyone else, and nothing is kept once you close the page.
How does it work out the thickness of the spine?
For paperbacks it multiplies your page count by Amazon KDP’s published per-page figure: 0.002252 inches for white paper and 0.0025 inches for cream paper. A 300-page book on white paper is 0.676 inches thick. The hardcover is a drawing approximation, not a KDP figure.
What size should my cover image be?
Use the front cover only, as large as you have it, because a bigger file gives a sharper mockup. Leave the trim on Auto and the book takes the shape of your image. Pick a KDP trim size (5 × 8, 5.25 × 8, 5.5 × 8.5 or 6 × 9 inches) and the cover is cropped from the middle to match it.
Can I use the pictures in ads, on my website and in my newsletter?
They are pictures of your own cover, made on your own device. We add nothing to them and claim no rights in them. The small Book Ad Pack credit is off unless you tick it.
Is a mockup enough for book ads?
A mockup shows your book; it does not make a stranger stop scrolling. It is the right picture for your website, newsletter header, preorder page and launch-day posts. For paid ads the picture usually has to show the story, which is what Book Ad Pack builds from your manuscript.